34,533 research outputs found

    Animal emergence during Snowball Earths by thermosynthesis in submarine hydrothermal vents

    Get PDF
    Darwin already commented on the lateness in the fossil record of the emergence of the animals, calling it a valid argument against his theory of evolution^1^. This emergence of the animals (metazoans: multicellular animals) has therefore attracted much attention^2-5^. Two decades ago it was reported that extensive global glaciations (Snowball Earths) preceded the emergence^6-7^. Here we causally relate the emergence and the glaciations by invoking benthic sessile^8-11^ thermosynthesizing^12-13^ protists that gained free energy as ATP while oscillating in the thermal gradient between a submarine hydrothermal vent^14^ and the ice-covered ocean. During a global glaciation their size increased from microscopic to macroscopic due to the selective advantage of a larger span of the thermal gradient. At the glaciation's end the ATP-generating mechanisms reversed and used ATP to sustain movement. Lastly, by functioning as animal organs, these protists then through symbiogenesis^15-17^ brought forth the first animals. This simple and straightforward scenario for the emergence of animals accounts for their large organ and organism size and their use of ATP, embryo and epigenetic control of development. The scenario is extended to a general model for the emergence of biological movement^18^. The presented hypothesis is testable by collecting organisms near today's submarine hydrothermal vents and studying their behaviour in the laboratory in easily constructed thermal gradients

    The Changing American Hospital in the Twenty-first Century 14th Annual Herbert Lourie Memorial Lecture on Health Policy

    Get PDF
    One is always hesitant to speak about the future. A famous philosopher from New York, Yogi Berra, said "Making predictions is difficult, especially about the future," and I have some trepidation about doing so now. There is also the difficulty of understanding what really has happened in the past. I recall the Bolshevik general in 1917 who said "The future is clear, but the past is very murky." We anticipate the future with more clarity than is justified, even as we disagree on what is happening right now or what happened before. In that vein, I will describe the role of the American hospital in our health care system, and the challenges it must meet, reviewing first the murky past by summarizing trends that have made hospitals what they are today.

    The miracle as a randomization device: a lesson from Richard Wagner's romantic opera Tannhauser und der Sankerkrieg auf Wartburg

    Get PDF
    In this paper we provide textual evidence on the sophistication of medieval deterrence strategies. Drawing on one of the great opera librettos based on medieval sources, Wagner’s Tannhäuser, we shall illustrate the use of optimal randomization strategies that can be derived by applying notions of dominance or trembling-hand perfection. Particular attention is paid to the employed randomization device
    • …
    corecore